Hi all,

[Rayw]

I have more or less decided to buy either a 10" or 12" Dob, I live in Perth and the only place I have found where I can actually go in a shop and buy one is BTOW in Malaga, so first question is there any other places that I have missed ? , I plan to use the telescope mainly at home and travel to a dark site maybe once a month/6 weeks, so portability is not an issue if I decide to go for the 12", on the BTOW web site they only advertise the Truss type for the 12" which I don't need, I am wondering if the openness (is that a word ha ha !!) of the Truss design will be more affected by light pollution , prices given at BTOW are $849 for the 10" and $1100 for the 12" am I going to see much difference between the 10/12" , my main interest is DSO's, lastly ...for now :) which Collomation tool would you recommend :thanx:

Ray.

[vanwonky]

Hi Ray, I am also new to this so I won't chime in on the tech stuff but it does seem BTOW is the one and only shop with a good range of scopes. I believe that some of the larger camera chains may do a few but with limited knowledge. There is a solid tube 10" DOB for sale in Perth in Gumtree at the moment for $650. Claims only 2 uses. Is it just me or does that seem be a common number with used telescopes! I am looking at the GOTO version so am not interested unless the price drop a bit with that one.
Cheers Dave

[Rayw]

Hi Dave,
I think you are right, I have done some more googling this morning for Telescope shops and came up empty !
Thanks for the heads up on the 10" I will check it out ,

Ray

[Osirisra]

BTOW is the only dedicated shop in Perth with pretty good prices and good service. For DSO's aperture is king so go for the biggest you can get and comfortably use. There is nothing wrong with the truss units and you just a bit of material like rubber matting and a bit of Velcro and you can slap up a shroud for less than 50 bucks easily. Made mine for my 14" and just made another one for my friends 10".

[Rayw]

Thanks Ken,
I will look into the rubber matting + velcro :thumbsup:

Cheers
Ray.

[Osirisra]

Clark rubber is a good place to get all the goodies ya need. ya want dense foam not rubber btw even thos I said rubber..but it like rubber :)

[Rayw]

I'm with ya:thumbsup:

[stevejack]

Hi Ray,

Keith at BTOW will sort you out, and you can see them in action at one of their viewing nights. Or there is also a place in Midland (Midland Camera House) where I got my scope from. They have several set up and the main guy there seems to know the stuff he's selling, he delivered mine (14" GOTO skywatcher) for free and offered to answer any questions. I'm pretty sure the same guy runs the website universalcameras.com.au with the prices of the scopes listed. This was the cheapest (local) price I could find at the time.

I bought my old 10" dob from Andrews (online store) and would do so again, no problems there.

Good luck, let us know how you get on.

[stevejack]

Just to follow up - Go the 12" if you can afford it. It will make a difference for the DSOs. I use a basic laser collimator to get things close if I'm just checking out a planet or the moon, and then if the seeing is really good and I'm going for DSOs I'll finish off with a catseye autocollimator. I only got the autocollimator when I picked up the 14", on the 10" dob I just used the Laser (barlowed) and was happy enough.

[Rayw]

Thanks for the info Steve, BTOW is not far from me so I will call in later this week to check things out, and I will follow your advice and go for the 12"

I am getting excited now :)

Thanks again,
Ray.

[Rayw]

Called in at BTOW today and had a good chat with Keith , he has the 12" for $1100, I also called Midland Camera House and they wanted $1375, so I will pick up the 12" from Keith next week, I asked about a Laser collimator $150 and he mentioned that the Laser also needs collimating before use ? I didn't get chance to ask why or how, I have been reading about collimating and am getting more confused as I read more ha ha !! you mentioned you use the Laser (barlowed), can you explain what the barlow does, (i know it is a doubler for eyepieces )

Cheers
Ray

[Rolf]

Hi Ray, Just a heads up about Btow. If you need replacement parts or something is missing with your scope you will have a hard time if not impossible time getting them. The customer after service sucks. Been waiting over a year for parts. Just keeps telling me stories that its been ordered..always told to come back but nothing happens...Never again !!! My friends and I have missed so much astro because of them..

[Rayw]

Sorry to hear you are having problems with Btow Rolf, as it turns out I have ordered from another source, so hopefully they deliver :eyepop:

[joecool]

Hi,
Collimation - I don't know about smaller newtonians with longer focal lengths (slow f ratio), but my 16" at f/4.5 (fast f ratio) is fairly critical in collimation. It does not help that the truss design is extremely floppy. Moving from vertical to the southern cross sort of altitude will move a laser from the center mirror spot to about 10mm off the spot. Theoretically I need to be within 1/3mm of the center of that spot for good viewing... The mirror cell springs need beefing up and the truss needs stiffening.

Well, I got a HoTech 2" / 1.25" SCA Laser Collimator with Crosshair, and an Astro Systems Collimating Tool Set which includes a Light Pipe/Sight Tube and the Autocollimator.

I used the lightpipe to adjust the secondary and focuser. On my scope the focuser needed 2mm of card on one side to tilt it to square with the secondary! Wowsa. But the cheapskates who built it used a 10" focuser base on a 16" tube so it never fitted properly anyway. I also used the laser which showed that the focuser was pointing about 15mm off center of the secondary when i have measured the secondary as being centered in the tube!

Once setup for viewing each time I use the laser to point the secondary at the center spot on the main mirror, though with a solid tube this should not move much if any at all, and then adjust the collimation knobs under the primary mirror to point the laser back at the 45degree plate in the laser and then do a double check that the laser is still centered in the ring on the primary.

I can double check this alignment with the Autocollimator. I must admit I've only had it for a week, but it has been spot on every time, so I reckon this laser is the way to go. The SCA arrangement centers the laser in the focuser with repeatability, and the 45degree viewing window means you can see the laser from the back end where you are collimation the primary and can do the collimation on your own, and the crosshair model means you can still see where the laser spot is when it falls into the lasers own hole and can get closer with the collimation than with a spot only laser.

Oh, and as the mirror cools I start seeing what looks like coma creeping towards the center and have to re-collimate a few times through the night, so having the laser to do this without shining torches down the tube and having to have someone help me is brilliant. And when I want to look at Saturn which is prominent at the moment, collimation is critical for any scope, more so than when looking at a wide field.

$145 for the laser and $80 for the 2 collimators and about $50 for express postage. I ordered them Thursday and had them Monday, though that time can sometimes push out to 2 weeks. d'oh.

Check out his guys site. One of the best descriptions I've seen.
http://www.propermotion.com/jwreed/ATM/Collimate/Collimate.htm

And check out the manufacturers site for a description of the Autocollimator
http://www.astrosystems.biz/coltlsm1.htm

and the laser
http://www.hotechusa.com/category-s/22.htm

Mark.

[Rayw]

Hi Mark

Thank you very much for all the info and links, very helpful for a newb like me :thumbsup:

Ray,